add-typep-transformer

This function is called for its side effects. The return value has
no meaning. This function tells the compiler that a typep form:

(typep x 'type)

can be transformed into the form:

(funcall predicate x)

The compiler will make the transformation where possible.

type must be a type, typically defined by the
user with deftype.
predicate should be a function object or a symbol
naming a function. That function must accept any Lisp object as a
single argument and return nil if the object
is not of type type, true if
it is of type type. remove-typep-transformer removes the
transform.